Some properties of corn starches II: Physicochemical,gelatinization, retrogradation,pasting and gel textural properties

The physicochemical, thermal, pasting and gel textural properties of corn starches from different corn varieties (African Tall, Ageti, Early Composite, Girja, Navjot, Parbhat, Partap, Pb Sathi and Vijay) were studied. Amylose content and swelling power of corn starches ranged from 16.9% to 21.3% and 13.7 to 20.7 g/g, respectively. The enthalpy of gelatinization (ΔH_gel) and percentage of retrogradation (%R) for various corn starches ranged from 11.2 to 12.7 J/g and 37.6% to 56.5%, respectively. The range for peak viscosity among different varieties was between 804 and 1252 cP. The hardness of starch gels ranged from 21.5 to 32.3 g. African Tall and Early Composite showed higher swelling power, peak, trough, breakdown, final and setback viscosity, and lower ΔH_gel and range of gelatinization. Pearson correlations among various properties of starches were observed. Gelatinization onset temperature (T_o) was negatively correlated to peak-, breakdown-, final- and setback viscosity (r = −0.809, −0.774, −0.721 and −0.686, respectively, p < 0.01) and positively correlated to pasting temperature (r = 0.657, p < 0.01). ΔH_gel was observed to be positively correlated with T_o, peak gelatinization temperature and (T_p) and gelatinization conclusion temperature T_c (r = 0.900, 0.902 and 0.828, respectively, p < 0.01) whereas, it was negatively correlated to peak- and breakdown- (r = −0.743 and −0.733, respectively, p < 0.01), final- and setback viscosity (r = −0.623 and −0.611, respectively, p < 0.05). Amylose was positively correlated to hardness (r = 0.511, p < 0.05) and gumminess (r = 0.792, p < 0.01) of starch gels.     

Relationships Between Selected Properties of Starches from Different Corn Lines

Starch was isolated from the corn lines obtained by crossing two different germ pools (MS and Tux pool) and evaluated for amylose content, swelling power, solubility, water binding capacity (WBC) and syneresis. The gelatinization (T_o, T_p, T_c, ΔH_gel, PHI & R) and pasting (pasting temperature, peak viscosity, breakdown viscosity, final viscosity and set back) properties of starches were measured using Differential Scanning Calorimeter (DSC) and Rapid Visco Analyzer (RVA), respectively. The relationships between different properties were also determined using pearson correlation coefficients. Amylose content was negatively correlated to swelling power and WBC (p < 0.05). Several significant relationships were also observed between thermal and pasting properties of isolated starches. Transition temperatures (T_o, T_p & T_c) and PHI showed positive correlation with peak, trough and breakdown viscosity (p < 0.05). Syneresis of starches was positively correlated to amylose content (p < 0.05).     

Effect of Amylose Content on Gelatinization,Retrogradation and Pasting Properties of Flours from Different Cultivars of Thai Rice

Presently, rice cultivars are categorized according to amylose content into three groups: low, medium and high amylose content cultivars. The correlation of amylose content with gelatinization properties, retrogradation, and pasting properties of eleven cultivars of Thai rice were investigated. Rice flour was prepared from milled rice by the wet grinding process. Onset (T_o), peak (T_p) and conclusion (T_c) temperatures of gelatinization, (determined by DSC) were found to be highly positively correlated with amylose levels. This correlation could be used for prediction of amylose content of rice flour. Low amylose starch could also be characterized by low degree of retrogradation (%R). The data obtained from RVA‐viscograms (peak viscosity, breakdown, setback, and pasting temperature) can be used only for characterization of the group of low amylose starches (waxy rice). It was demonstrated that low amylose rice starch provided the highest peak viscosity and breakdown and the lowest setback and pasting temperature among the groups investigated.     

Some properties of corn grains and their flours I: Physicochemical,functional and chapati-making properties of flours

The variability in physical (1000 kernel weight and bulk density) and mechanical (rupture force) properties of grains from different Indian corn varieties (African tall, Ageti, Early composite, Girja, Navjot, Parbhat, Partap, Pb sathi and Vijay) were studied. The functional (colour, gelatinization, retrogradation and pasting) and chapati-making properties of flours milled from corn varieties were evaluated. African tall flour showed the highest enthalpy of gelatinization (ΔH_gel), peak-, trough-, breakdown-, final-, and setback viscosities, and L^∗ (84.4) value and resulted in chapaties with higher extensibility (5.76 mm) and of light colour. African tall flour, with the lowest protein content, showed the lowest grain rupture force. Amylose content and hardness of starch gel from African tall were found to be the lowest among all corn varieties. Girja flour, with the lowest transition temperatures and ΔH_gel, showed the lowest extensibility of chapaties made from it. Pearson correlations between physical and textural properties of corn grains and the functional properties of their flours were established. Rupture force of corn grain and protein content of flour showed a negative correlation with peak viscosity of flour (r = −0.917, and −0.863, p < 0.01). The protein content of flours was negatively correlated with L^∗ (r = −0.759, p < 0.01) value and positively with b^∗ (r = 0.635, p < 0.01) value. Pasting temperature of flours showed a significant negative correlation with peak, trough, breakdown, final and setback viscosities (r = −0.836, −0.846, −0.778, −0.871, and −0.847, respectively, p < 0.01). Pearson correlation was also established between the grain and starch properties. Rupture force of corn grains was positively correlated with the amylose content of starch (r = 0.950, p < 0.01).     

Relationships Between Selected Properties of Seeds,Flours, and Starches from Different Chickpea Cultivars

ABSTRACT

Five desi (PBG-1, PDG-4, PDG-3, GL-769, and GPF-2) and one kabuli type (L-550) chickpea cultivars were evaluated for their seed mass, volume, hydration capacity, swelling capacity, cooking time, and instrumental textural properties (hardness, cohesiveness, gumminess, and chewiness). Flour was prepared from these chickpea cultivars and various physicochemical and functional properties were determined. The pasting (pasting temperature, peak viscosity, breakdown, and final viscosity) and gelatinization (T _o, T _p, T _c, and ΔH _gel) properties of these flours were measured using Rapid Visco Analyzer (RVA) and Differential Scanning Calorimeter (DSC), respectively. Starch was also isolated from chickpea cultivars and evaluated for amylose content, swelling power, solubility, and syneresis values. Physicochemical, cooking, and instrumental textural properties of seeds of different chickpea cultivars were related to physicochemical, gelatinization, and pasting properties of their flours and physicochemical properties of their starches. Selected properties of chickpea seeds were significantly correlated with the properties of their starches and flours. Hardness value of soaked chickpea seeds was positively correlated to cooking time, seed mass, seed volume, hydration, and swelling capacity (p < 0.01). Water solubility index (WSI) of chickpea flours was positively correlated to seed mass, volume, hydration capacity, and hardness value (p < 0.05). Selected instrumental textural parameters of seeds had positive correlation with ΔH _gel of flours (p < 0.01). Peak viscosity of flours showed positive correlation to breakdown, final viscosity, bulk density, and negative correlation to cohesiveness of soaked seeds (p < 0.01). Final viscosity showed negative correlation to bulk density and water absorption index (WAI) (p < 0.01) of flours.     

Gelatinization and Pasting Properties of Waxy and Non‐waxy Rice Starches

Gelatinization and pasting properties of diverse rice types grown in two locations were examined by differential scanning calorimetry (DSC) and rotational rheometry, respectively. The data were compared to previously reported molecular starch properties for these samples: specifically, amylose content, starch molecular weight (M_w), and amylopectin side‐chain‐length distributions. Significant correlations were observed between amylose content, starch M_w, and the weight degree of polymerization of the long side chains of amylopectin F₁(DP_w) and many of the gelatinization and pasting properties measured. Higher amylose content corresponded with increased gelatinization onset (T_o) and peak temperatures (T_p), pasting onset and peak temperatures, and decreased peak and trough viscosity. Starch M_w correlated negatively with T_o, T_p, pasting onset, and peak temperature and positively with peak, trough, final, and breakdown viscosity. Amylopectin with DP_w 59‐78 of F₁(DP_w) correlated with increased T_o, T_p, pasting onset and peak temperature, and decreased peak, trough, final and breakdown viscosity. Pasting properties were also somewhat related to DP_w 21 of shorter side chains of amylopectin (F₂(DP_w)). Significant correlations between F₂(DP_w) and peak, final, and breakdown viscosity were observed (r = −0.447*, −0.391*, −0.388*, peak, final, and breakdown viscosity, respectively).     

Starch properties as affected by sorghum grain chemistry

To determine the relationship between sorghum grain polyphenol content, grain structure, and starch properties, starch was isolated from 10 sorghum varieties using an alkali steep and wet‐milling procedure. SV2, a tannin‐free variety with white pericarp, gave a white starch. Varieties having red or white pericarp and higher polyphenol levels gave pink starches. Hunter colour values (L, a, b) of starches were not correlated with grain polyphenol content. Grain appearance in terms of pericarp colour, or presence or absence of pigmented testa, did not relate to the intense pink colouration of sorghum starches. Starch amylose content was significantly negatively correlated (r = −0.88, p < 0.001) to grain floury endosperm texture. Sorghum starches had higher peak viscosity (PV) in pasting than commercial maize starch. The time taken to reach peak viscosity from the initial viscosity rise was less for sorghum starches than maize starch. However, sorghum starches had a higher rate of shear thinning (R_st) than maize starch. There was a significant positive correlation between grain polyphenol content and starch PV (r = 0.75, p < 0.05). Starch gel hardness was negatively correlated to pasting properties of R_st and paste breakdown (r = −0.78 and −0.77 respectively) at p < 0.01. Peak gelatinisation temperature (T_p) occurred over a narrow range from 66 to 69 °C. T_p was negatively correlated to the floury endosperm portion of the grain (r = −0.77) at p < 0.01. It is concluded that sorghum grain polyphenol content and grain characteristics influence its starch properties. © 2000 Society of Chemical Industry     

Physicochemical,Thermal, Morphological and Pasting Properties of Starches from some Indian Black Gram (Phaseolus mungo L.) Cultivars

The starches separated from thirteen different black gram cultivars were investigated for physicochemical, thermal, morphological and pasting properties. Amylose content, swelling power, solubility and water binding capacity of starches ranged between 30.2–34.6%, 16.0–22.3 g/g, 14.8–17.3% and 73.5–84.5%, respectively. The diameter of starch granules, measured using a laser‐light scattering particle‐size analyzer, varied from 12.8 to 14.3 μm in all black gram starches. The shape of starch granules varied from oval to elliptical. The transition temperatures (T_o, T_p and T_c) and enthalpy of gelatinization (ΔH_gel) determined using differential scanning calorimetry, ranged between 66.1–71.3, 71.0–76.2, 75.9–80.4°C and 6.7–9.4 J/g, respectively. Pasting properties of starches measured using the Rapid Visco Analyser (RVA) also differed significantly. Pasting temperature, peak viscosity, trough, breakdown, final viscosity and setback were between 75.8–80.3°C, 422–514, 180–311, 134–212, 400–439 and 102–151 Rapid Visco Units (RVU), respectively. Turbidity values of gelatinized starch pastes increased during refrigerated storage. The relationships between different properties were also determined using Pearson correlation coefficients. Amylose content showed a positive correlation with swelling power, turbidity and granule diameter. Swelling power showed a negative correlation with solubility and setback. T_o, T_p and T_c showed positive correlation with turbidity, pasting temperature and were negatively correlated to peak and breakdown viscosity.     

Physicochemical and Gelatinization Properties of Starches Separated from Various Rice Cultivars

Morphological, viscoelastic, hydration, pasting, and thermal properties of starches separated from 10 different rice cultivars were investigated. Upon gelatinization, the G′ values of the rice starch pastes ranged from 37.4 to 2057 Pa at 25 °C, and remarkably, the magnitude depended on the starch varieties. The rheological behavior during gelatinization upon heating brought out differences in onset in G′ and degree of steepness. The cultivar with high amylose content (Goami) showed the lowest critical strain (γ_c), whereas the cultivars with low amylose content (Boseokchal and Shinseonchal) possessed the highest γ_c. The amylose content in rice starches affected their pasting properties; the sample possessing the highest amylose content showed the highest final viscosity and setback value, whereas waxy starch samples displayed low final viscosity and setback value. The onset gelatinization temperatures of the starches from 10 rice cultivars ranged between 57.9 and 64.4 °C. The amylose content was fairly correlated to hydration and pasting properties of rice starches but did not correlate well with viscoelastic and thermal characteristics. The combined analysis of hydration, pasting, viscoelastic, and thermal data of the rice starches is useful in fully understanding their behavior and in addressing the processability for food applications.     

In vitro Starch Digestibility and Nutritionally Important Starch Fractions in Cereals and Their Mixtures

Dietary carbohydrates are characterized with respect to both chemical composition and likely site, rate and extent of digestion. Starch is divided into rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS). The present investigation aimed at evaluating the effect of starch source on nutritionally important starch fractions and the extent of in vitro starch digestion in four processed cereals, namely rice, ragi (Eleusine coracona), wheat, jowar (Sorghum vulgare) and their mixtures in varying proportions, using controlled enzymatic hydrolysis with pancreatin and amyloglucosidase. Rapidly available glucose (RAG) was also measured to derive a starch digestion index (SDI). The total starch and amylose content in the raw cereals ranged from 21 — 26.6 and 12.6 — 20.7 g/100 g, respectively. Among the four basic cereals, roti (flat, unleavened pancake, diameter 12 cm) produced from ragi had highest total starch, RDS and SDI. However, in mixtures containing two or more cereals RDS and SDI were lower than those observed in single cereals. Significant correlations were observed between RAG and SDI, or RDS, respectively (r=0.91, r=0.96, p<0.01). An inverse relation between amylose content and SDI (r= ‐0.78, p<0.01) indicates the influence of amylose on the extent of starch digestion. The results highlight the importance of starch source in determining the starch fractions of processed cereals and their mixtures. The simple in vitro measurement of starch fractions could serve as a tool for characterizing dietary carbohydrates with respect to their digestion in the gut.     

Physicochemical properties and structure of starches from Chinese rice cultivars

Starches from 10 different non-waxy rice cultivars in China were isolated and investigated for their physicochemical properties including the swelling power, solubility, syneresis, thermal, rheological and textural properties, and structure. The range of amylose content in 10 rice starches was between 18.1 and 31.6%. The branch chain length distribution of amylopectin revealed that the proportions of short (DP6–11), medium (DP12–17), and longer chains (DP18–23) were 4.6–11.1%, 47.0–51.6% and 25.3–31.8%, respectively. The relationships between different properties of rice starches were determined using Pearson correlation analysis. Amylose content was negatively correlated to swelling power (r = ?0.632, p ≤ 0.05) and positively correlated to gel hardness (r = 0.776, p ≤ 0.01). The percentage of short chains (DP6–11) was negatively related to the transition temperatures (T_o, T_p and T_c), T_oG′ and T_G′max, while the percentage of medium chains (DP12–23) was positively related. Various branch chain length amylopectins played different roles in rheological behavior of starch dispersions. The percentage of short chains (DP6–11) was positively correlated to G′ and G″(r = 0.832 and r = 0.775, respectively, p ≤ 0.01), and negatively correlated to tanδ peak (r = ?0.717, p ≤ 0.05). However, the percentage of longer chains (DP18–23) showed a negative relation with G′ and G″ (r = ?0.794, p ≤ 0.01; r = ?0.741, p ≤ 0.05), and a positive relation with tanδ peak (r = 0.668, p ≤ 0.05).     

Relationships between various physicochemical,thermal and rheological properties of starches separated from different potato cultivars

Various physicochemical, thermal and rheological properties of starches separated from Indian potato cultivars were related to each other using the Pearson correlation. Amylose content, water‐binding capacity (WBC), swelling power, solubility, ash content, transmittance, syneresis and consistency coefficient (K) were determined. Amylose content was significantly correlated with swelling power (r = 0.904), transmittance (r = 0.656) and syneresis (r = 0.777) of the starches. Thermal properties such as transition temperatures (T_o, T_p and T_c), gelatinisation range (R), gelatinisation enthalpy (ΔH_gel) and peak height index (PHI) of the starches were measured using differential scanning calorimetry (DSC). T_o, T_p and T_c were positively correlated with swelling power and negatively correlated with solubility and WBC. PHI was positively correlated with WBC and negatively correlated with ash content and swelling power. R had a negative correlation with WBC (r = ?0.726) and PHI (r = ?0.737). A positive correlation between R and T_c was observed. WBC was negatively correlated with swelling power (r = ?0.749). Syneresis of potato starches was positively correlated with transmittance, ash content, swelling power and amylose content. K was positively correlated with amylose content (r = 0.587). The results showed a significant variation in various functional and thermal properties of starches separated from different potato cultivars. Copyright © 2004 Society of Chemical Industry     

Physicochemical Properties of Caribbean Sweet Potato (Ipomoea batatas (L) Lam) Starches

The proximate compositions and physicochemical properties of 21 Caribbean sweet potato (Ipomoea batatas (L) Lam) starches were investigated. Proximate composition, amylose, reducing and non-reducing sugars were determined using standard methods. Swelling power and solubility were evaluated and pasting properties of the starches were determined using Rapid Visco Analyzer. Moisture (8.0–12.4%), protein (0.0–0.2%), ash (0.1–0.5%), and reducing (0.3–2.3%) and non-reducing sugar (0.1–0.2%) contents of starches were significantly different (P < 0.05) among the cultivars. Amylose content varied significantly between 12.8–21.3%. Swelling power and solubility ranged between 7.8–31.1% and 1.5–9.6%, respectively. Pasting properties such as peak viscosity measured in Rapid Visco Units (143.2–288.8 RVU), breakdown viscosity (29.4–162.6 RVU), and setback viscosity (15.0–78.8 RVU), pasting temperature (73.5–87.7 °C) and time to pasting temperature (3.6–4.5 min) varied significantly among the cultivars. Breakdown viscosity was poorly correlated with final viscosity attained (r = − 0.0507, P < 0.05); however, pasting temperature was correlated (r = 0.479, P < 0.05) with setback viscosity. The variability observed in the physicochemical properties of the starches was related to specific requirements for use in the production of noodles, pasta, and inclusion in bread and weaning food formulations.     

Starch from hull-less barley: II. Thermal,rheological and acid hydrolysis characteristics

Gelatinization, granular swelling, amylose leaching, viscosity and acid susceptibility characteristics of starches isolated from 10 hull-less barley (HB) genotypes [zero amylose (CDC Alamo), waxy (CDC candle, SB 94794, SB 94912, and SB 94917), normal amylose (Phoenix, CDC Dawn, SR 93102, and SB 94860) and high amylose (SB 94893 and SB 94897)] were monitored by differential scanning calorimetry (DSC), swelling power (SP), solubility, Brabender viscoamylography, and reaction with 2.2 N HCl (at 35 °C), respectively. DSC data showed that T_o, T_p, T_c, T_c–T_o, and ΔH ranged from 50.1–56.1, 58.1–64.5, 71.0–75.8, 17.9–24.0 °C and 9.6–14.2 J/g of amylopectin, respectively. In compound waxy (SB 94917) and compound normal (SR 93102 and SB 94860) starches, T_o and T_c–T_o were lower and higher, respectively, than in the other starches. ΔH followed the order: compound normal>waxy>normal≈zero amylose>high amylose>compound waxy. The SP followed the order: zero amylose>waxy>compound normal>normal>high amylose. A rapid increase in solubility occurred at lower temperatures (<70 °C) for zero amylose HB starch, however, this increase was gradual for the other starches. At 90 °C, solubility followed the order: high amylose>compound normal>normal>waxy. Zero amylose and waxy HB starches exhibited lower pasting temperatures, higher peak viscosities, and higher viscosity breakdown than normal HB starches. The extent of acid hydrolysis followed the order: zero amylose>compound waxy>waxy>normal>compound normal>high amylose. High correlations were observed between physicochemical properties and structural characteristics of HB starches.     

Differences in physicochemical properties of kernels of two rice cultivars during grain formation

BACKGROUND: Rice varieties with similar apparent amylose content may have different grain qualities. The development of rice quality is a dynamic process that occurs with the formation of rice kernels. In this study, physicochemical properties during the grain formation period were investigated to interpret differences in grain quality between two non‐waxy rice cultivars, Wuyujing3 and 30you917, with similar apparent amylose content. RESULTS: There were significant differences in dynamic changes in 1000‐grain weight, amylose content and pasting and thermal properties during grain formation of the two cultivars. The difference in their apparent amylose contents from 5 days after anthesis (DAA) to 15 DAA was significant, except in the late grain‐filling stage. Wuyujing3 showed a slower increase in 1000‐grain weight than 30you917 from 10 to 25 DAA. The transition temperatures (T_o, T_p and T_c) of developing grain flour of Wuyujing3 were higher than those of 30you917 during the grain formation period. Wuyujing3 showed greater stickiness (higher breakdown and peak viscosity and lower positive setback) than 30you917 according to Rapid Visco Analyser (RVA) profiling. CONCLUSION: The results suggested that the differences in cooking and eating quality parameters of the two mature rices were determined by the differences in grain filling and the dynamic changes in the main rice quality components such as amylose content, grain weight and differential scanning calorimetry and RVA properties, which will help cultivators understand the physical basis of rice quality development. Copyright © 2011 Society of Chemical Industry     

Changes in functional characteristics of starch during water caltrop (Trapa Quadrispinosa Roxb.) growth

This study was carried out to establish the changes of physicochemical properties of Taiwan’s water caltrop (Trapa Quadrispinosa Roxb.) starch at various stages of maturity during growth. Investigations showed that the dry matter and starch contents of water caltrop increased from 9.7% to 25.61% and from 49.4% to 79.4% (d.b.), respectively, as growth progressed (from 14th to 42nd day after fruit development). The shape of the starch granules was smooth, oval and poly-angular during the growth period. The granule size of starch increased with increase of physiological age, ranging from 19.4 μm to 32.2 μm. The X-ray diffraction patterns could be classified as a typical A-type crystalline structure. Swelling power and solubility of water caltrop starch increased with increases of growth time. Starches obtained from water caltrop at the early stage exhibited a lower gelatinization temperature (T_o, T_p, T_c) and gelatinization enthalpy (ΔH) than did the late stage of maturity. The rapid viscosity analyzer (RVA) parameters suggested that water caltrop starch paste had a low breakdown, and appeared to be thermo-stable, at the early harvest time. The pasting temperature, peak viscosity, final viscosity and setback value of water caltrop starch increased as growth progressed. Different starch granular size and amylose content could be the major factors influencing starch physicochemical properties during maturity.     

Effects of different crop starches on the cooking quality of Chinese dried noodles

To investigate the effects of seven starches made from different crop sources on noodle quality, Chinese dried noodles made from various reconstituted flours were prepared and analysed. Potato starch had better solubility and swelling power than the other starches, leading to higher water absorption, cooking loss and breakage ratio of the potato starch noodles. The correlation results unravelled that the cooking breakage ratio of noodles presented positive correlations with solubility, swelling power, peak viscosity (PV), trough viscosity (TV) and final viscosity (FV) values of starches. Besides, the adhesiveness of noodles showed a positive correlation with conclusion temperature (T_c) and setback viscosity (SV) values of starches. Moreover, the peak temperature (T_p) value of starches was negatively correlated with cooking loss; the granule size of starches had a positive correlation with noodles water absorption; and the peak time (PkT) value of starches represented positive relationships with noodles chewiness, shearing force and breaking strength.     

Characterisations of kabuli and desi chickpea starches cultivated in China

The characterisation of starches from kabuli and desi type chickpea seeds was investigated by monitoring amylose content, swelling power, solubility, synaeresis, water-binding capacity and turbidity properties. Total amylose and apparent amylsoe content were 31.80% and 29.93% for kabuli and 35.24% and 31.11% for desi, respectively. The shape of starch granules varied from round to oval or elliptic. The transition temperatures (T_o, T_p and T_c) were (62.237, 67.000 and 72.007 °C) and (59.396, 68.833 and 77.833 °C) for kabuli and desi starches, respectively. The ΔH value of kabuli type was higher than that of desi type. The crystal type of chickpea starches was a typical C_A-type pattern. Breakdown and setback viscosity of kabuli starch were lower than those of desi starch, indicating high heat and shear stability. Kabuli starch showed a higher value of M_w (5.382 × 10⁷ g/mol) than desi starch (3.536 × 10⁷ g/mol). Both kabuli and desi starches belonged to low glycaemic starches from measuring starch fractions and hydrolysis index.     

Effect of water stress at different stages of grain development on the characteristics of starch and protein of different wheat varieties

The effect of water stress (WS) at 8 and 15 days post anthesis (DPA) on the characteristics of starch and protein separated from C-306, HD-2329, PBW-175, PBW-343 and NI-5439 wheat varieties was studied. WS-induced changes in A-, B- and C-type granules distribution were variety- and stage-dependent. A-type granules increased in response to WS at both stages in all varieties, the extent of increase being greater at 15 DPA. The proportion of B-type granules decreased in all the varieties, except C-306, in response to WS at 15 DPA. C-type granules also decreased in response to 15 DPA in all varieties, except HD-2329. The starch from wheat exposed to WS at 15 DPA showed lower amylose content, lipids content and pasting temperature, and higher peak viscosity, final viscosity and setback. DSC analysis of starches showed two endotherms (associated with the melting of crystallites and amylose–lipid [AML] complexes) during heating, and an exotherm (associated with reforming of AML) during cooling. Transition temperatures (T_o, T_p and T_c) of AML dissociation and association were lower for starch from wheat exposed to WS, the effect being more at 15 DPA. The changes in pasting and thermal properties of starch caused by WS were observed to be related to lipids, amylose content and distribution of granules. The effect of WS on accumulation of different dimethyl formamide-soluble and insoluble proteins was significant and variety dependent.     

Influence of Heat‐Moisture Treatment and Acid Modifications on Physicochemical,Rheological, Thermal and Morphological Characteristics of Indian Water Chestnut (Trapa natans) Starch and its Application in Biodegradable Films

Water chestnut starch was subjected to acid modification and heat‐moisture treatment. Hydrochloric acid was used for acid modification at three different concentrations (0.25 M, 0.5 M and 1 M) for 2 h. Modifications did not alter the granule morphology. Heat‐moisture treatment (HMT) resulted in slight reduction in the granular size of the starch granules. Acid modification lowered the amylose content, swelling power, water‐ and oil‐binding capacity but improved the solubility of starch to a considerable level. Light transmittance of acid‐modified (AM) starches improved significantly. A significant reduction in peak, trough, final and setback viscosity was observed by acid‐thinning. In case of heat‐moisture treated starch the final viscosity (F_v) was found to be even higher than the peak viscosity (P_v). Native water chestnut starch exhibited a lower onset temperature (T_o) and peak temperature (T_p) of gelatinization than the corresponding acid‐treated starches. Starch films prepared from native starch exhibited excellent pliability, whereas those prepared from AM and HMT starches showed good tensile strength. Starch films prepared from acid‐treated starches provided better puncture and tensile strength.